Exam 2 Quiz 1 Flashcards
Population Ecology
The study of how and why population size, structure, and distribution patterns change over time
Population definition
a group of individuals of the same species in a particular area so they can potentially interact
*you potentially could interact with everyone here at Luther
Why study populations?
-to understand what factors affect/might be influencing population increase or decrease
-to make predictions about change in populations in the future
-effectively manage populations (wildlife) through hunting and fishing
Distribution
where are members of the population located?
Abundance
how many individuals are there in the population?
Range
the entire geographic area where members of a species are found
*affected by abiotic and biotic factors
-contains overexploitation, habitat loss, and extirpation
Biotic factors that affect bobcat range and therefore abundance and distribution?
1) food availability (PREY): squirrels in forests and rabbits in prairies
2) competition for space (territoriality)
Abiotic factors that affect bobcat range and therefore abundance and distribution?
1) snowfall- bobcats can’t walk on snow far North, lynx have adaptation of big feet and can
2) overexploitation
3)habitat loss
4) extirpation
some ovals hate Eli
Overexploitation
-over harvesting (bobcat fur in midwest)
-not enough being born to replace those killed
-need a sustainable population
Habitat Loss
conversion of forests and prairies in 1800’s to cropland of corn and soybeans ELIMINATED PREY
Extirpation
a localized extinction
-species exists in parts of range but extinct in others
Quantifying Abundance- How do we determine population size?
Census and Sampling
Census
count every individual in the population
-works well for small populations of organisms that are visible and easy to see
Sampling Def
a way to estimate population size of smaller animals that are hard to count, take samples
sample: a subgroup of a population
Types of Sampling
1) Mark-Recapture
2) Plots
3) Quadrants
4)Transects
Mark-Recapture Sampling
mark 100 bobcats, release them, capture 50, 10 of them are already marked, what’s the estimate size of the population?
Lincoln Index: N= Mxn/m
N- size of population
M- # marked initially
n- # of all individuals in 2nd sample
m= # of marked ind from 1st sample in 2nd sample
100x50/10 = 500
Plot Sampling
Used to sample large ares
ex: trees in HRW
-Center point and 8 m circle out from that to get 200 m2
Quadrant Sampling
used for smaller organisms in smaller areas, like plants in a 1m by 1m square
-let us calculate density, percent cover, and biomass
Demography
the study of how population changes over time, space, ect
Models
help is understand and describe change in a population
Population growth model
what affects population size?
births (natality) and immigration increase
deaths (mortality) and emigration decrease
EXPONENTIAL GROWTH
population growth model
dN/dt = rN (population growth rate)
N- number of ind in the population (pop size)
dN- d is the change and dN is the change in population size
t- time (min, sec, years)
dt- change in time
what is “r”? formula?
The per capita rate of increase (per capita means ‘for each ind in the pop’)
r=b-d
b=birthrate or number of births
d= death rate or number of deaths
r= number of individuals added to or subtracted from population per individual in population
r=0
population neither increasing or decreasing, stable
r>0
population increasing, more births than deaths
r<0
population decreasing, more deaths than births
*without immigration will decrease more
exponential growth and r on the chart?
a high ‘r’ will make a steeper j-shaped curve
a small population of fruit flies has the same per capita rate of increase (r) as a large population of fruit flies, if everything else is equal why will the large population add more individuals per unit of time?
-start with 10 fold the amount of population
-at different point in the curve
-higher up on the y-axis for “N” the sooner the line will hit the slope
trends for exponential growth on a graph (3)
N vs t graph- population size over time (assume n>0)
dN/dt vs N graph- population growth rate/size of population
r vs N plot- where r=1/N * dN/dt (rate isn’t changing)
N vs t graph- population size over time (assume n>0)
j shaped curve, N on y axis, t on x axis
-as time increases, population increases, and population rate gets steep er
dN/dt vs N graph- population growth rate/size of population
diagonal line going ip
-dN/dt on y axis, N on x axis
-rate doesn’t change but the size of the population increases
r vs N plot- where r=1/N * dN/dt (rate isn’t changing)
straight line starting halfway up y axis going straight across
-r on y axis, N on x axis
-rate isn’t changing
is the exponential growth model useful?
it’s unrealistic because it is assuming there are unlimited resources, it can’t increase forever
For exponential growth you need founders in a new habitat- what are founders?
ex) endangered elephant, only two left, population begins to roe
What is an “annual restart” and how does it relate to exponential growth?
every year in a population just a few individuals survive through the winter with many resources that decrease as more reproduce and population grows again
-every yr exponential growth occurring
-invasive species
ex) monarchs, bumblebees
Why do populations get “knocked back” (eventually re-bounce and add to exponential growth)
-harsh winter, habitat loss, excessive hunting, disease, hurricane
*creates an empty habitat that then a population can explode in
Why don’t populations grow exponentially forever?
resources are limited
-competition for resources
-these factors affect birth and death rates (b and d)
what is “carrying capacity” in exponential growth?
K= the maximum number of individuals in a population that can be maintained by the available resources
-the “ideal” population size
LOGISTIC GROWTH uses the …
logistic growth model
Logistic growth model formula
dN/dt= r * (k-n/k) *N
*this new addition influences “r”, the individual rate of population growth, Dn/dt
N=population size
In logistic growth, how does (K-N)/K affect r and dN/dt when N is very small?
-if N0=10, K=1,000
1,000-10/1,000
-about 1
*minimal impact on intrinsic per capita rate of increase and population size (almost no impacts)
In logistic growth, how does (K-N)/K affect r and dN/dt when N is very large?
-if N=900 and K=1000
1000-900/1000
-about 0.1
In logistic growth, how does (K-N)/K affect r and dN/dt when N>K?
-you get a negative number which makes population growth decrease
On a logistic growth curve, where is r the slowest and fastest?
slowest at top part of “S” curve, fastest at the bottom start of it
On a logistic growth curve, where is dN/dt largest?
on the going up part of the “S” curve
after population burst and run out of resources, when can ? be positive again?
once N gets below K again
see notes for clicker question
how many trend graphs for logistic growth?
3
N vs t graph (assume r>0)
-dashed K at top, classic “S” curve with N on y axis and t on x axis
dN/dt vs N plot
-frowny face with peak in middle of graph
-dN/dt on y axis and N on x axis
-curve starts at N0 and ends at K
r vs N plot (because of K-N/K)
line starting from top diagonally down to lower right
-r on y axis
-N on x axis
-N0 at 0 on x axis and K at very far right on x axis
Examples of logistic growth
-sheep in Tasmania: carrying capacity in environment can fluctuate year to year based on environment
-fur seals in st Paul island, Alaska: K fluctuates a bit depending on resources
What makes the population growth rate (dN/dt) change as N increases?
dN/dt (rate of population increase) will slow as N increases towards K
Density Dependent Factors
intensity of impact increase as population grows ( as N increases, intensity increases)
-competition for food, shelter, space, mates
-Disease, stress, parasites, predation
*impact is dependent on population size
Fecundity
potential for reproduction, measured by r= per capita rate of increase (# of offspring have)
how many offspring produced
*fecundity decreases as density (N) increases
Density Indepedant Factors
things that impact b and d rates, independent of population size
-can knock back size of a population
ex) doesn’t matter how many people are in FL, hurricane still impacted them
-storms, drought, fire, landslides, volcanoes, severe winters
Why do we use such simple population growth models?
to understand what happens with population
-models make many simplifying assumptions but can also make some general conclusions
Key assumptions for both exponential and logistic growth models
1) models are influenced by initial conditions
ex) what is N0?
2) models assume constant conditions
environmental stochasticity
seemingly “random” environmental conditions that affect the models
at low N, environmental stochasticity may do what?
drop population below min population size (N0) causing extirpation or extinction
Life History Strategies
-how individuals allocate their resources (energy/time) for developmental growth, ability to reproduce, and survival
-diff species make diff choices and this affects their fitness because RESOURCES ARE LIMITED
fitness
ability of an individual to produce viable and fertile offspring in comparison to others in a population
Life History Continuum (r-K continuum)
-its impossible to maximize growth, reproduction, AND survival
-you must choose
r- selection populations
r-selected species: exhibit traits that are more advantageous at low N (high r)
-age at first reproduction is early
-short life span
-short maturation time
-often high Mortality rate
-many offspring produced per reproductive episode
-little or no parental care
-small size of offspring
K- selection populations
K-selected species: exhibit traits at are advantageous at high N near K (very low r)
-age at first reproduction is late
-long life span
-long maturation time
-low mortality rate
-few offspring produced per reproductive episode
-often extensive parental care
-large size of offspring
Population Age Structure has 3 aspects
-life tables
-survivorship curves (Nt vs age)
-age pyramids
Life tables
way of describing the probability an individual is going to survive and reproduce at different ages (various age classes)
cohort
a group of individuals of the same age followed from birth/hatching to death
-1000 ind of proportion alive at beginning of each age class (min, yr, days, etc)
Description of life table columns letters to know
x
Nx
lx
mx
Ro
x
age class (unit of age)
Nx
number of individuals alive at the start of the age class
lx
survivorship, proportion of ind alive at the start of the age class
mx
age specific fecundity, how many offspring produced by an individual alive during an age class
Ro
Net reproductive rate=E lx * mx
Survivorship Curves (3)
Type I,II,III
Type I survivorship curve
high survivorship, low fecundity
*characteristics of k selected species
ex) humans, dolphins
Type II survivorship curve
die more or less squally throughout their lifespan across all age classes
ex) many birds
Type III survivorship curve
high fecundity but low survivorship
*r-selected species
ex) fish, trees, insects
Age pyramids
graph out lx and Nx from life tables
-if even, pop stable
-more at top than bottom- declining
-more at bottom than top- increasing
community definition
all of the population of species that interact with one another in a given area
Interspecific interactions
-interaction between species have impact on fitness, 4 types
+/0
commensalism, one species benefits, other species unaffected
ex) cattle egret/bison
+/+
mutualism, both species benefit
ex) plants/bees or clownfish/sea anemone
-/-
competition, both species suffer and decrease fitness
ex)bear and wold fight over bison carcass
+/-
consumption, one species benefits, other suffers (through predation, herbivory, parasitism)
ex) bald eagle/fish or tick/human
niche
range of resources a species uses to survive, grow, and reproduce
resources can be biotic or abiotic and found in gradients
biotic- food, pollinators, food size
abiotic- space, water, temp, sunlight, nutrients
resources are multidimensional
each species needs multiple resources (3d-10d)
competition
2 species trying to use the same resource, use or defense of a resource that reduces its availability to another species
what happens when two species compete?
the outcome depends on the amount of niche overlap
-neither benefits from the competition unless one who outcompetes the other to extinction lives in the end and has resource all to itself
niche overlaps have two types
partial overlap and complete overlap
partial overlap
competition occurs for some common resource both species need but species can still SHARE the resource in the overlap of the niches
complete overlap
2 species use the same niche
ex) paramecium, Neanderthals, invasive species
Fundamental niche
the theoretical range of resources a species could use
realized niche
the fundamental niche a species actually uses when in competition
niche differentiation (aka: resource partitioning)
competition leads to changes in traits of competing species so both species survive and competition is decreased
ex) galapogos finch
community structure: how do ecologists describe communities?
1) composition
2) structural complexity
3) roles of species in communities
composition
-what species are present?
-species richness (S)
-relative abundance/evenness (J’)
-diversity, shannon index (H’)
structural complexity
the physical shapes and sizes of the species present in a community and how they fit together
4 types
Typical plant community structure
-seen from tallgrass prairies to tropical rainforest
-leaf litter/herbaceous layer and course woody debris
-canopy
-understory
-emergents
leaf litter/herbaceous layer and course woody debris
(spring wildflowers and seeds here)
-on the ground
canopy
full grown trees, the height of the forest
understory
small trees growing below canopy
emergents
few individuals that grow above the canopy
Roles of species in communities
a) trophic roles
b) trophic relationships
Trophic roles
autotrophs and heterotrophs
autotrophs
(self-feeders) carry out photosynthesis, conversion of light energy to chemical energy in the form of glucose
PRODUCERS- “coverters”
heterotrophs
(other feeders) organisms that eat another organism to obtain chemical energy
CONSUMERS
3 TYPES OF HETEROTROPHS
-herbivores
-predators and parasites
-decomposers/detritivores
herbivores
plant eaters
predators and parasites
eat other animals
decomposers/detritivores
organisms that eat detritus
detritus
dead and decaying organic matters (animals, fungi)
trophic relationships have three aspects
-food chain
-food web
-trophic levels
food chain
living from primary producer to primary decomposers or consumer, to 2nd consumer and on and on
Trophic level: where on the food chain do you eat
food web
all of the integrating species at different trophic levels exchanging energy and nutrients
trophic levels
1st- producers
2nd- herbivores
3rd and up- predators
are all species equally important
how to determine abundance, dominance, biomass, keystone species, top down control, and trophic cascades
Abundance
how many ind. in a given area?
dominance
what species dominates through its size
ex) basal area
Are all species equally important?
no, some are keystone species
Keystone
a plant or animals that plays a unique role in the community and it exhibits a disproportional influence relative to its abundance- on how the community functions
ex) sea otters in kelp forests
Top-Down Control
a species at a higher trophic level (sea otter) influences distribution and abidance of species at lower trophic levels
-predator limits prey
Top down control causes
trophic cascades
trophic cascades
a series of changes in the abundance and distribution of species in a food web/community caused by ADDITION or REMOVAL of a keystone species
-results in dramatic change in community structure and nutrient cycling
-ex: wolves in Yellowstone National Park
-have a big network
ecosystem engineers
create niches/habitats for other species
ex) beaver
what is a disturbance
a short lived disruption to bring a biological community that rebuilds species or changes the abundance of different species or changes the distribution of resources in the community
Types of Disturbances
Natural and Anthropogenic
natural disturbances
fire, wind, ice, blizzard. drought, landslides,earthquake, volcanoes, glaciers, FLOODS
Anthropogenic disturbances
“human caused”
ex) fire, development of housing, invasive species introduction, air pollution, global warming, habitat fragmentation, FLOODs from dams
frequency
how often to disturbances occur
*see chart
-not all disturbances happen at the same frequency and have the same level of impact on a community
severity
how intense is the impact of the disturbance?
-vary in intensity and impact
ex: high intensity crown fire vs low intensity surface fire
scale of disturbance
how big is the area that is being disturbed?
ex: bison wallows
Disturbance Regimes
-what is the regular pattern of disturbances in a community?
Tall grass praire disturbances
fire and grazing
Grand Canyon disturbances
annual spring flood now is artificially replicated because of dam
Intermediate Disturbance Hypothesis
Species diversity will be highest in communities with intermediate levels of disturbance (disturbance regime)
Succession
the sequential development, or recovery, of communities after a disturbance
-2 types
primary succession
when a disturbance removes the organisms and the soil from the surface
ex) intense fire, flood, landslide, volcano
secondary succession
reeves most of organisms but leaves the soil
ex) cooler fire, logging, grazing, windstorms
successional pathway
the sequence of species over change following a disturbance
pioneer species
typical first species to show up (weeds)
steps of successional pathways
1) Pioneering species (abandoned agriculture field .weeds/wind)
2) early successional community (longer lived herbaceous)
3) mid-successional communities (shrubs and short lived trees)
4) late successional communities (long lived trees, temperature forest)
what is the primary factor that influences species richness on a global scale
latitude
global patterns need to be
stable
latitude
distance N or S from equator
latitudinal species richness gradient
shows that life is most abundant and diverse in the tropics
local patterns
larger ares with more species than smaller area
species-area relationships def
the number of species found within an area in relation to are of the habitat *area affects species richness ?
species-area relationships equation and graph
S=cA^z
S= number of species
c=y intercept?
A=area
z= slope of line?
*S is dependent on A?
-a loglog scala in a straight line with number of species on the y axis, and area in miles squared on the x axis going up into right hand corner? can it curve?
what explains this relationship btwn area and species richness?
The theory of island biogeography
who wrote the theory of island biogeography?
MacArthur and Wilson in 1967
What is the heory of island biogeography?
the number of plant and animal species on an island is related to the area of the island’s landmass and degree of isolation
*species richness is higher on larger islands and nearshore islands
*species richness is lower on smaller, isolated islands
aspects that make up the theory of island biogeography?
immigration
extinction
emigration ???
island equilibrium model
rates of immigration or extinction on y axis, number of species on the island on x axis immigration starts at top and curves down, extinction starts at bottom and curves up
-the meeting point is the equilibrium point
equilibrium point
the expected number of species in a community???
What influences immigration and extinction rates?
-species richness depends on island size and remoteness
-larger/near islands have high imm rates and low extinction rates
-smaller/remote islands have low immigration rates and high extinction rates
SIZE of the island
-bigger islands have bigger resources
-rate of imm increases as size increases (more resources, niches, habitats, topography)
-rate of extinction decreases as island size increases??? decreases??? more space to co-exist???
size of the island graph
rate of immigration or extinction on the y axis, small island and large island paint, and number of species on island for x axis
-see chart, I’m sorry
DISTANCE from mainland
if an island is closer to shore, it’s easier for species to find it
-same thing, there’s also a remote and near block on the y axis
the usefulness of island biology
larger parks have lower extinction rates
-prairies here are islands in farmland
-national parks/preserved areas importance
metapopulations
-population of populations (subgroup)
-regional group of connected populations of a single species
-dynamic: extinction and recolonization of local population is common, will re-introduce to extinct area island
-due to habitat fragmentation, more species forced into the population structure
ex) Otto skippers on Hill Prairies in NE IA (48.7% loss since 1980s)
principles of conservation reserve design
-based on theories of island biogeography
-larger reserve, completely protected, wildlife bridges, more resources, unfragmented
ex) Y2Y initiative- Yellowstone to Yukon
but still….. fragmentation is an issue that causes
habitat loss and degradation
edge effect
abrupt transitions between habitats
